bug#51821: 29.0.50; Suggest add variable or frame parameter: line-height

[Feng Shu]

Eli Zaretskii <eliz@gnu.org> writes:

>> From: Lars Ingebrigtsen <larsi@gnus.org>
>> Cc: "Feng Shu" <tumashu@163.com>,  51821@debbugs.gnu.org
>> Date: Sun, 14 Nov 2021 18:55:38 +0100
>> 
>> Eli Zaretskii <eliz@gnu.org> writes:
>> 
>> > So what would be the correct interpretation of the line-height
>> > variable or frame parameter, when different faces are being used?
>> 
>> I think...  a natural interpretation would be that explicit :height
>> specs would override the line-height variable/parameter?
>
> But line-height is not a variable or parameter, it is just a text
> property, and it needs to be put on a newline to change the height of
> that single line.  So currently this is up to the Lisp program: if it
> puts this property on some line, the visual results is its
> responsibility.
>
> By contrast, a buffer-local variable or a frame parameter are global:
> they apply to all lines, tall and small alike.  And users will use
> this variable/parameter globally as well.  Thus its effect on lines
> that use smaller fonts is something to be concerned about.
>
> My impression is that this is wanted only for the default face, and
> then only for the ASCII font of that face.  That could be done, I
> think, but (a) it will probably not work with text-scaling and other
> remappings of the default faces, and (b) some faces other than default
> also need this, definitely the mode-line and header-line, but also
> fixed-pitch perhaps?
>
> So I'm stuck trying to figure out what exactly are the requirements
> here.

What about support it as a face attr instead of variable?


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